The present invention relates to a process for the preparation of a supported olefin polymerization catalyst composition, comprising a support optionally treated with an organometallic compound, a metallocene, and an alumoxane. The invention also relates to a supported olefin polymerization catalyst composition which has been prepared according to said process and to the use of such a supported olefin polymerization catalyst composition for the polymerization of at least one olefin.
In many olefin polymerization processes using a single site catalyst, it is desirable to support the catalyst on a carrier or support. Usually such supported catalyst compositions include a metallocene and an alumoxane supported on an inorganic oxide carrier such as silica and/or alumina.
For example, WO 96/00243 describes a method for producing a supported catalyst composition by mixing a bridged bis-indenyl metallocene and an alumoxane in a solvent to form a solution, and then combining the solution and a porous support, whereby the total volume of the solution is less than that at which a slurry is formed. A typical support used was previously heated silica MS 948 (Grace) and a typical alumoxane used was gel-free methyl alumoxane (MAO), both of which were used in all of the examples.
According to S. Srinvasa Reddy, Polymer Bulletin, 36 (1996) 317-323, the ethylene polymerization activity of tetraisobutyldialumoxane cocatalyst was clearly lower than the activity of methylalumoxane cocatalyst. This reflects the previous general opinion, that only methyl alumoxane as a cocatalyst gave satisfactory ethylene polymerization catalyst activities.
In the present application a catalyst system has been described where the catalyst composition comprises a support optionally treated with an organometallic compound, a metallocene, and an alumoxane. Now it has been realized that when an aluminium oxide support and a metallocene with at least one silyl substituent in the cyclopentadienyl ring are used in polymerization with an alumoxane as an external cocatalyst, the polymer morphology does not meet the requirements when using the known polymerization methods. When alumoxane with large molecular size, like hexaisobutylalumoxane, is used as an external cocatalyst, it has difficulties to diffuse evenly into a very porous catalyst particle, which causes the polymerization to start from the surface of the catalyst particle where the alumoxane is capable to activate the metallocene. Because polymerization starts only at the surface of the catalyst particle, an uncontrolled break down of the catalyst takes place and causes high risk for reactor fouling and inhomogenous polymer. Also when a high molecular weight alumoxane is used as an external coactivator in a gas phase process, there is a tendency of the solvent of the alumoxane to evaporate forming a solid alumoxane. When the coactivator becomes solid, it has no possibilities to enter into the metallocene catalyst pores and it is not anymore able to activate metallocene compounds.
The purpose of the present invention is to improve the quality of the product when metallocenes with at least one silyl substituent in the cyclopentadienyl ring are used with a non-methyl alumoxane in olefin polymerization. More specifically, the present invention aims at providing an olefin polymerization catalyst composition including a metallocene with at least one silyl substituent in the cyclopentadienyl ring and a C2-C12 alkyl alumoxane, which has commercially satisfactory activity when producing olefin homopolymers and copolymers. A further goal of the present invention is a supported olefin polymerization catalyst composition for use in gas phase, slurry phase or liquid/solution phase polymerizations.
The above mentioned purposes of the invention have now been realized by a novel process for the preparation of a supported olefin polymerization catalyst composition, comprising a porous carrier optionally treated with an organometallic compound, a metallocene, and an alumoxane. If an alkylated metallocene is used, the carrier need not to be treated with an organometallic compound. The porous carrier is preferably an inorganic oxide, most preferably a silicon dioxide. The claimed process comprises mainly impregnating a support comprising a solid compound being a porous carrier, previous to or immediately before the beginning of the olefin polymerization, in any order, optionally with
a) an organometallic compound of the general formula (1):
R1MXvxe2x88x921xe2x80x83xe2x80x83(1)
xe2x80x83wherein each R is the same or different and is a C1-C10 alkyl group; M is a metal of Group 1, 2, 12 or 13 of the Periodic Table (IUPAC 1990); each X is the same or different and one of a halogen atom, a hydrogen atom, a hydroxyl radical or a C1-C8 hydrocarbyloxy group; 1 is 1, 2 or 3; v is the oxidation number of the metal M,
and with a complex solution of at least
b) a metallocene of the general formula (2):
(CpY)mMxe2x80x2Xxe2x80x2nZoxe2x80x83xe2x80x83(2)
xe2x80x83wherein each CpY is the same or different and is one of a mono- or polysubstituted, fused or non-fused, homo- or heterocyclic cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, or octahydrofluorenyl ligand, the ligand being covalently substituted at its cyclopentadienyl ring with at least one substituent Y which is one of a xe2x80x94ORxe2x80x2, xe2x80x94SRxe2x80x2, xe2x80x94NRxe2x80x22, xe2x80x94CRxe2x80x2xe2x95x90, or xe2x80x94PRxe2x80x22 radical, each Rxe2x80x2 being the same or different and being one of a tri-C1-C8 hydrocarbyl silyl group or a tri-C1-C8 hydrocarbyloxy silyl group; Mxe2x80x2 is a transition metal of Group 4 of the Periodic Table and bound to the ligand CpY at least in an xcex75 bonding mode; each Xxe2x80x2 is the same or different and is one of a hydrogen atom, a halogen atom, a C1-C8 hydrocarbyl group, a C1-C8 hydrocarbylheteroatom group or a tri-C1-C8 hydrocarbylsilyl group or two Xxe2x80x2 form a ring with each other; Z is a bridge atom or group between two CpY ligands or one CpY ligand and the transition metal Mxe2x80x2; m is 1 or 2; o is 0 or 1; and n is 4-m if there is no bridge Z or Z is a bridge between two CpY ligands or n is 4-m-o if Z is a bridge between one CpY ligand and the transition metal Mxe2x80x2, and
c) an alumoxane of the following general formulas (3): 
xe2x80x83wherein each Rxe2x80x3 and each Rxe2x80x2xe2x80x3 is the same or different and is a C2-C12 alkyl group; and p is an integer between 1 and 40,
and recovering said supported olefin polymerization catalyst composition.
At step (a) the support can be treated for example with an aluminiumalkyl to alkylate the support. However, when an alkylated metallocene compound is used, the alkylation of the support is not needed. When an alkylated metallocene is used it is advantageous to treat the support by heat for removing some hydroxyl groups from the surface of the carrier particle.
By mono- or polysubstituted is meant that, in addition to said substituent Y, there may optionally be other substituents at the rings at said ligands CpY.
By fused or non-fused is meant that any ring at said ligands may be fused or non-fused, i.e. have at least two atoms in common, with at least one further ring.
By homo- and heterocyclic is meant that any ring of said ligands may have only carbon ring atoms (homo- or isocyclic) or may have other ring atoms than carbon (heterocyclic).
It has thus been realized that a C2-C12 alkyl alumoxane (i.e. a non-methyl alumoxane) can successfully be used as an internal coactivator, if a support comprising a porous carrier is treated with a solution of metallocene having at least one silyl substituent at the cyclopentadienyl ring and with a non-methylalumoxane based alumoxane. It is advantageous first to treat the porous carrier particle with an organometallic compound to alkylate the surface of the particle. However, this is not needed if a alkylated metallocene is used.
According to a non-limiting model, said electron pair of double bond substituents at the cyclopentadienyl ring delocalize it""s negative charge and help to ionize the metallocene, whereby the transition metal M becomes more cationic (electron density deficient). This improves the catalytic interaction between the metallocene and the alumoxane and enables the use of higher alumoxanes like those of the above formula (3).
Generally, said support can be contacted with compounds b) and c), and optionally a), in any order. Thus, the support can e.g. be impregnated with a solution of the three compounds a), b) and c), preferably first with compound a) and then with a solution containing compound b) and compound c).
According to one embodiment of the invention, the contacting of the support with compounds a), b) and c) takes place by firstly contacting the support with a solution of said organometallic compound (1) and thereafter with a solution containing said metallocene (2) and said alumoxane (3). In one preferable embodiment of the invention, the contacting takes place by
a1) contacting said support with a solution of said organometallic compound (1), and removing the supernatant from the contacting product,
b1) contacting the product of step a1) with a a complex solution of said metallocene of formula (2) and of said alumoxane of formula (3), and removing the supernatant from the contacting product.
When contacting said support with compounds a, b and c in liquid form such as the form of a solution, a slurry or a non-slurry contacting product can be formed. However, it is preferable to impregnate the support with a liquid, the volume of which is less than at which a slurry is formed. This means that the volume of said liquid is less than or approximately equal to the volume of the support pores.
The support used in the process of the present invention is a porous carrier, preferably an inorganic oxide, for example pure silicon dioxide. According to the invention a porous carrier particle gives high-activity olefin polymerization catalysts when combined with a C2-C12 alkyl alumoxane according to formula (3) and a metallocene according to formula (2). The material carrying said solid compound can be any inert porous particulate material, including silica. The most preferable support comprises a porous silicon dioxide, which has been heated to a temperature between 90-1000xc2x0 C. The silicon dioxide, preferably calcined silica, is preferentially in the form of, or deposited on, particles having a diameter of between 10-500 xcexcm, most preferably between 20 and 200 xcexcm. The specific surface area of the silicon dioxide is according to one embodiment of the invention between 50 and 600 m2/g, preferably between 100 and 500 m2/g. The average pore volume is usually between 0.5 and 5.0 ml/g, preferably between 1.0 and 2.5 ml/g. The average pore diameter is for example 100-500 xc3x85, preferably approximately 200 xc3x85.
According to one embodiment of the process of the present invention, the support is contacted with an organometallic compound of the general formula (1):
R1MXvxe2x88x921xe2x80x83xe2x80x83(1)
wherein each R is the same or different and is a C1-C10 alkyl group; M is a metal of Group 1, 2, 12 or 13 of the Periodic Table; each X is the same or different and one of a halogen, a hydrogen atom, a hydroxyl radical or a C1-C8 hydrocarbyloxy group; 1 is 1, 2 or 3; and v is the oxidation number of the metal M.
According to a non-limiting theoretical model, the organometallic compound deposited on the carrier material alkylates the carrier surface, which in turn alkylates the metal of the metallocene compound. If the metallocene compound is already alkylated, there is no need for alkylation of the carrier. These alkylated siloxy substituted metallocenes are reflected in the successful use of otherwise poorly active higher alumoxanes.
The C1-C10 alkyl group R of formula (1) is preferably a C1-C6 alkyl group and most preferably a C1-C4 alkyl group. When defining M by means of the Groups and Periods of the Periodic Table, the new numbering system is used (IUPAC 1990). Preferred metals M are those of Periods 1-4 of the Periodic Table.
If occuring, X of formula (1) is a halogen atom, a hydrogen atom, a hydroxyl radical or a hydrocarbyloxy group. According to one embodiment of the invention, said support is contacted, provided that the metallocene of the general formula (2) is not alkylated, with said organometallic compound of the general formula (1), which is one of a C1-C10 alkyl lithium, a C1-C10 dialkyl magnesium, or a C1-C10 trialkyl aluminium, and most preferably is a C1-C6 trialkyl aluminium such as trimethyl aluminium (TMA). When contacting said support with said organometallic compound, it is preferable if the organometallic compound of the formula (1) is immersed or dissolved in a hydrocarbon medium, most preferably a C4-C10 hydrocarbon medium. The weight ratio between the added organometallic compound, calculated as trimethyl aluminium, and the support depends on the surface area, pore volume and diameter, surface hydroxyl number and type. According to one embodiment it is between 0.1 and 10, more preferably between 0.2 and 2 and most preferably between 0.3 and 1.5. After the contacting step the remaining unreacted organometallic compound is preferably removed together with the possible hydrocarbon medium, followed by optional washing steps.
According to the process of the present invention said support is contacted with a metallocene of the general formula (2). It is preferred that the metallocene of the general formula (2) as group Rxe2x80x2 of said substituent Y has a tri-C1-C8 hydrocarbyl silyl or tri-C1-C8 hydrocarbyloxy silyl group. Especially suitable tri-C1-C8 hydrocarbylsilyl groups are those capable of xcfx80 interaction with said O, S, N, or P atoms of Y. Most preferred are tri-C1-C8 alkyl silyl groups, wherein at least one of the C1-C8 alkyl is a branched C3-C8 alkyl group such as isopropyl, isobutyl, sec-butyl, tert-butyl, isoamyl, sec-amyl, tert-amyl, isohexyl, sec-hexyl, or tert-hexyl. Cyclic alkyls and aryls are also preferred groups of the silicone atom.
According to one embodiment of the invention there is only one ligand CpY in the metallocene of formula (2), which preferably is bound to the transition metal Mxe2x80x2 by both said xcex75 bond and by a bridge Z preferably containing a heteroatom.
However, said metallocene of the general formula (2) has most preferably two ligands CpY, i.e. m is 2. According to a still more preferred embodiment, the two CpY ligands are bridged with each other by a bivalent atom or group Z having at least one chain atom which is one of a carbon, silicon, oxygen, sulphur, nitrogen, or phosphorus atom. Most preferably, the metallocene of the general formula (2) has m=2, whereby Z is an ethylene or a silylene bridge.
The transition metal Mxe2x80x2 of group 4 of the Periodic Table in the general formula (2) is Ti, Zr or Hf, more preferably Zr or Hf, and most preferably Zr. The valency or oxidation number of Mxe2x80x2 is 4.
In the definition of Xxe2x80x2 above, a heteroatom means 
The preferable atom or group Xxe2x80x2 of said metallocene of formula (2) is a halogen atom and/or a C1-C8 hydrocarbyl group. Most preferably, Xxe2x80x2 is chlorine and/or methyl. The number of Xxe2x80x2 atoms or groups, i.e. xe2x80x9cnxe2x80x9d, is preferably 1-3, most preferably 2, considering the limitation given above for the case when Z is a bridge between CpY and Mxe2x80x2.
Particularly preferred metallocenes of the general formula (2) are compounds of following structural formula (4). 
wherein Y1 and Y2 are the same or different and are one of a hydrogen atom, a halogen atom, an acyl group, an acyloxy group, a C1-C10 hydrocarbyl group, a xe2x80x94ORxe2x80x2, xe2x80x94SRxe2x80x2, xe2x80x94NRxe2x80x2, xe2x80x94C(H or Rxe2x80x2)xe2x95x90, or xe2x80x94PRxe2x80x22 radical, Rxe2x80x2 being a tri-C1-C8-hydrocarbylsilyl group, provided that at least one of Y1 and Y2 is one of said xe2x80x94ORxe2x80x2, xe2x80x94SRxe2x80x2, xe2x80x94NRxe2x80x2, xe2x80x94CRxe2x80x2xe2x95x90, or xe2x80x94PRxe2x80x22 radicals; Z is a bivalent atom or group having at least one chain atom which is one of a carbon, silicon, oxygen, sulphur, nitrogen or phosphorus atom, preferably 1-4 carbon and/or silicon chain atoms; each Rv is the same or different and is one of a hydrogen atom, a halogen atom, a C1-C10 hydrocarbyl group or ring constituent, or a C1-C10 hydrocarbyloxy group, Mxe2x80x2 is one of Ti, Zr or Hf; and Xxe2x80x21 and Xxe2x80x22 are the same or different and are one of a halogen atom and a C1-C8 hydrocarbyl group. The analogous 4,5,6,7-tetrahydroindenyl derivatives are also useful in the invention.
A representative metallocene of the formula (2) is ethylene-bis(2-tert-butyldimethylsiloxyindenyl)zirconium dichloride.
When using chiral metallocenes, they can be used as a racemate for the preparation of highly isotactic xcex1-olefin polymers. The pure R or S form of said metallocene can also be used, e.g. for the production of optically active polymer.
The metallocene of the general formula (2) is usually prepared by a process involving repeated deprotonations/metallizations of the aromatic ligands and introduction of the bridge Z atom or atoms as well as the central atom by their halogen derivatives. The preparation of the said metallocene of the general formula (2) can e.g. be carried out according to a J. Organometallic Chem. 288 (1958) 63-67 and EP-A-320762, both herewith incorporated by reference. See also Soares, J. B. P., Hamidec, A. E., Polym. Reaction Eng., 3 (2) (1995) 131-200, herewith incorporated by reference.
The most preferred metallocenes of the general formula (2), wherein Y is a tri-C1-C8 hydrocarbylsiloxy group, is preferably prepared as follows:
The catalyst compounds according to the invention can be prepared from 2-indanone. This compound can be reacted in a suitable solvent with a base and a chlorosilane to form 2-siloxyindene with a yield of over 80%. Suitable solvents are for example dimethylformamide (DMF) and tetrahydrofurane (THF). Suitable bases are for example imidazole and triethylamine (TEA). Suitable chlorosilanes are for example tert-butyldimethylchlorosilane, t-hexyldimethylchlorosilane and cyclohexyldimethylchlorosilane. The reaction takes place according to the following reaction scheme (II): 
According to one embodiment of the invention 2-tert-butyldimethylsiloxyindene is reacted first with butyllithium and then with dimethyl dichlorosilane (Me2SiCl2) to form dimethylsilylbis(2-tert-butyldimethylsiloxyindene). Butyllithium can be replaced with methyllithium, sodium hydride or potassium hydride. Likewise dimethyl dichlorosilane can be replaced with any dialkyl or diarylsilane. Silicon can be replaced with germanium.
Dimethylsilylbis(2-tert-butyldimethylsiloxyindene) can be reacted with butyllithium, which gives the corresponding bislithium salt. This product can be reacted with zirconium tetrachloride to yield dimethylsilylbis(2-tert-butyldimethylsiloxyindenyl)zirconium dichloride as a mixture of the racemic and meso diastereomers. Butyllithium may be replaced as described earlier. Zirconium tetrachloride can be replaced with titanium tetrachloride or hafnium tetrachloride to give the corresponding titanium and hafnium complexes. The reactions take place according to the following reaction schemes (III-IV): 
According to another embodiment of the invention 2-tert-butyldimethylsiloxyindene is reacted first with butyllithium and then with dibromoethane to form bis(2-tert-butyldimethylsiloxyindenyl)ethane. This compound can be reacted with two equivalents of butyllithium, which gives the corresponding bislithium salt. This can then be reacted with zirconium tetrachloride to yield ethylenebis(2-tert-butyldimethylsiloxyindenyl)zirconium dichloride. The racemic diastereomer of the latter is formed in great excess and is easily separated from the meso isomer by fractional crystallization. Catalytic hydrogenation of racemic ethylenebis(2-tert-butyldimethylsiloxyindenyl)zirconium dichloride yields the corresponding tetrahydroindenyl complex. The reactions takes place according to the following reaction scheme (V): 
In the reactions above butyllithium may be replaced as described earlier. Zirconium tetrachloride can be replaced with titanium tetrachloride or hafnium tetrachloride to give the corresponding titanium and hafnium complexes.
According to still another embodiment of the invention 2-t-hexyldimethylsiloxyindene is reacted first with butyllithium and then with dibromoethane to form bis(2-t-hexyldimethylsiloxyindenyl)ethane. This compound can be reacted with two equivalents of butyllithium which gives the corresponding bislithium salt. This can then be reacted with zirconium tetrachloride to yield ethylenebis(2-t-hexyldimethylsiloxyindenyl)zirconium dichloride. The racemic diastereomer of the latter is formed in great excess and is easily separated from the meso isomer by fractional crystallization. The reaction takes place according to the following reaction scheme (VI): 
In the reactions above butyllithium may be replaced as described earlier. Zirconium tetrachloride can be replaced with titanium tetrachloride or hafnium tetrachloride to give the corresponding titanium and hafnium complexes. Hydrogenation of ethylenebis(2-t-hexyldimethylsiloxyindenyl)zirconium dichloride yields the corresponding tetrahydroindenyl complex.
IIlustrative but non-limiting examples of the preferable metallocene compounds used according to the invention are, among others, racemic and meso dimethylsilylbis(2-tert-butyldimethylsiloxyindenyl)zirconium dichloride, racemic and meso diphenylsilylbis(2-tert-butyldimethylsiloxyindenyl)zirconium dichloride, racemic and meso dimethylsilylbis(2-t-hexyldimethylsiloxyindenyl)zirconium dichloride, racemic and meso diphenylsilylbis(2-t-hexyldimethylsiloxyindenyl)zirconium dichloride, racemic and meso dimethylsilylbis(2-cyclohexyldimethylsiloxyindenyl)zirconium dichloride, racemic and meso dimethylsilylbis(2-cyclohexyldimethylsiloxyindenyl)zirconium dichloride, racemic and meso dimethylsilylbis(2-2-tert-butyldiphenylsiloxyindenyl)zirconium dichloride, racemic and meso diphenylsilylbis(2-tert-butyldiphenylsiloxyindenyl)zirconium dichloride, racemic and meso dimethylsilylbis(2-tert-butyldimethylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, racemic and meso diphenylsilylbis(2-tert-butyldimethylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, racemic and meso dimethylsilylbis(2-t-hexyldimethylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, racemic and meso diphenylsilylbis(2-t-hexyldimethylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, racemic and meso dimethylsilylbis(2-cyclohexyldimethylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, racemic and meso diphenylsilylbis(2-cyclohexyldimethylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, racemic and meso dimethylsilylbis(2-tert-butyldiphenylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, racemic and meso diphenylsilylbis(2-tert-butylphenylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, rac-ethylenebis(2-tert-butylmethylsiloxyindenyl)zirconium dichloride, racemic and meso ethylenebis(2-t-hexyldimethylsiloxyindenyl)zirconium dichloride, racemic and meso ethylenebis(2-cyclohexyldimethylsiloxyindenyl)zirconium dichloride, racemic and meso ethylenebis(2-tert-butyldiphenylsiloxyindenyl)zirconium dichloride, rac-ethylenebis(2-tert-butyldimethylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, racemic and meso ethylenebis(2-cyclohexyldimethylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride, racemic and meso ethylenebis(2-tert-butyldiphenylsiloxy-4,5,6,7-tetrahydroindenyl)zirconium dichloride and rac-ethylenebis(2-t-hexyldimethylsiloxyindenyl)zirconium dichloride. Titanium or hafnium can be used instead of zirconium in corresponding complexes.
When contacting said support, comprising a solid compound being a silicon dioxide, with said metallocene of the general formula (2), the metallocene is preferably dissolved in a C4-C10 hydrocarbon solvent and most preferably in an aromatic hydrocarbon solvent such as toluene. As was said before, the metallocene hydrocarbons solution may also contain an alumoxane. The solution is then contacted with the support, which generally is porous.
It is also advantageous, if the total volume of the solution added to the support is less than the volume required to form a support slurry and, according to one embodiment, equal to or less than the pore volume of the support.
Although the amount of metallocene may vary much e.g. due to the structure of the support, according to one embodiment of the present invention, the support is contacted with said metallocene of the formula (2) at a molar to weight ratio between the metallocene and the support of between 0.001 to 0.50 mmol/g, more preferably 0.010 to 0.10 mmol/g, most preferably 0.02 to 0.08 mmol/g.
In the present process for the preparation of a supported olefin polymerization catalyst composition, the support comprising a solid compound being a porous carrier, such as pure silicon dioxide, is contacted with an alumoxane of the general formulas (3). Formulas (3) are general formulas including not only linear and cyclic compounds, but also alumoxane compounds of cage and net structures. See e.g. Harlan, et. al., J. Am Chem. Soc., 117, (1995) p. 6466, the alumoxane structures of which are enclosed by reference to disclose one embodiment of the invention. The alumoxane used in the process of the present invention is preferably an alumoxane (3), wherein said Rxe2x80x3, and optionally said Rxe2x80x2xe2x80x3 is a C2-C12 alkyl group, more preferably an isopropyl isobutyl, sec-butyl, tert-butyl, isoamyl, sec-amyl, tert-amyl isohexyl, sec-hexyl or tert-hexyl group. The most preferred alumoxane of the formula (3) is preferably an alumoxane in which 2xe2x89xa6pxe2x89xa612, most preferably 4xe2x89xa6pxe2x89xa68. A suitable alumoxane of the formula (3) is hexa(isobutylaluminiumoxane). The alumoxane according to the present invention can be prepared analogously to or by modifying a variety of methods for preparing alumoxane, non-limiting examples of which are described in U.S. Pat. Nos. 4,665,208, 4,952,540, 5,091,352, 5,206,199, 5,204,419, 4,874,734, 4,924,018, 4,908,463, 4,968,827, 5,308,815, 5,329,032, 5,248,801, 5,235,081, 5,157,137, 5,103,031, EP-A-0 561 476, EP-B1-0 279 586, EP-A-0 594 218 and WO 94/10180.
According to the invention the alumoxane is acting as an internal coactivator in the catalyst system. In order to introduce sufficient amount of alumoxane into the carrier pores it is preferable to use rather concentrated alumoxane solutions. Said support is contacted previous to or immediately before the beginning of the olefin polymerization, with an alumoxane of formula (3) dissolved or immersed in a hydrocarbon solvent, most preferably a C4-C12 aliphatic hydrocarbon solvent such as pentane. When contacting said support with said organometallic compound of the formula (1), said metallocene of the formula (2), and said alumoxane of the formula (3), the molar ratio between the alumoxane aluminium metal and the metallocene transition metal Mxe2x80x2 in the catalyst composition is preferably between 20 and 500, more preferably 30 and 300 and most preferably between 50 and 150.
When preparing a supported olefin polymerization catalyst composition according to the present invention, the contacting product between the support, the optional organometallic compound of the general formula (1), the metallocene of the general formula (2) and the alumoxane of the general formula (3) can be subjected to a prepolymerization with at least one olefin such as propylene and/or ethylene. The prepolymerizate is then recovered as said supported olefin polymerization catalyst composition.
In addition to the above described process for the preparation of a supported olefin polymerization catalyst composition, the present invention also relates to a supported olefin polymerization catalyst composition which has been prepared according to said described process. The invention also relates to a process for polymerizing at least one olefin by polymerizing in the presence of a supported olefin polymerization catalyst prepared according to the above described process. In the polymerization (homopolymerization and copolymerization) olefin monomers, such as ethylene, propylene, 1-butylene, isobutylene, 4-methyl-1-pentene, 3-methyl-1-butene, 4,4-dimethyl-1-pentene, vinylcyclohexene and their comonomers, can be used. Dienes and cyclic olefins can also be homo- or copolymerized. These xcex1-olefins and other monomers can be used both in the polymerization and prepolymerization of the claimed supported olefin polymerization catalyst composition.
The polymerization can be a homopolymerization or a copolymerization and it can take place in the gas, slurry or a solution phase. The claimed catalyst composition can also be used in high pressure processes. Said xcex1-olefins can be polymerized together with higher xcex1-olefins in order to modify the properties of the final product. Such higher olefins are 1-hexene, 1-octene, 1-decene, etc.